The present invention relates to the combination of a cutting apparatus designed to be operated at a remote location and means associated therewith for enabling an operator at a remote station to view and monitor the cutting operation in an optimum fashion. The invention is particularly designed to view and monitor the cutting of linings applied to conduits such as sewer pipes in order to provide access to conduits extending laterally therefrom.
As part of the rehabilitation of underground pipes and the like, such as sewer pipes, it is customary to provide a continuous lining along a given length of the pipe. The pipe will customarily have laterals extending therefrom, for example, to connect a sewer to users such as residences along the route of the pipe. The lining as initially applied usually covers those laterals and hence prevents communication therewith, which is inadmissible. The lining must therefore be removed from the opening to the lateral so that fluid communication with the lateral is restored. Since the opening to the lateral is remote from a main end of the pipe and since in many instances human access to the interior of the pipe is in any event impossible or extremely inconvenient, the cutting operation must be controlled from a remote station. Apparatus for performing such a cutting operation in such an environment is known, and typical embodiments thereof are shown in such patents as Davis et al. 4,197,908 of Apr. 15, 1980 entitled "Apparatus For Porting a Side Wall of a Conduit From Interiorly Thereof", Wood patent 4,442,891 of Apr. 17, 1984 entitled "Cutters", Wood patent 4,577,388 of Mar. 25, 1986 entitled "Method of Cutting Apertures in Lining in Underground Pipes", and Wood patent 4,701,988 of Oct. 27, 1987 entitled "Relating to Cutters". As will be seen from those representative patents, the cutters comprise a cutting element which can be moved into a pipe to the position where cutting is to be performed, after which the cutting element is actuated and moved to carry out the desired cutting operation. A television camera is also moved through the pipe along with the cutter, and that which it sees is conveyed electronically to a remote station where the movement of the cutting element is controlled. The TV camera is usually located along the axis of the main pipe at a distance of about two feet from the cutter and is stationary while the cutting element is moving to commence and carry out the cutting operation. Hence the view of the cutting operation that the operator at the remote station gets is far from optimum, and does not permit truly close manual control of the cutting operation.
It has been proposed in the past to provide a mirror designed to reflect the viewed action of the cutting element to a TV camera, but it has proved difficult to achieve an effective continuous view with such a mirror, and one advantage of the present invention is that it provides better continuous viewing with lower mass and mechanical inertia and occupying less space than the prior art mirrors.
The problem of cutting openings to laterals in the environment under discussion is complicated by the fact that the shape of the piece to be cut from the liner is neither a circle nor an ellipse, but is the intersection of two cylinders whose axes do not necessarily intersect and whose axes are not necessarily at right angles to each other. Because of the nature of this shape, the use of a fixed TV camera to monitor the cutting often gives a distorted view of the shape of the opening that must be cut from the liner.